U.S. patent application number 09/814689 was filed with the patent office on 2001-10-25 for engine valve operating system for internal combustion engine.
This patent application is currently assigned to Nissan Motor Co., Ltd.. Invention is credited to Adachi, Hidefumi, Hoshi, Yoshikazu, Yonekura, Koichiro.
Application Number | 20010032603 09/814689 |
Document ID | / |
Family ID | 18628356 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010032603 |
Kind Code |
A1 |
Yonekura, Koichiro ; et
al. |
October 25, 2001 |
Engine valve operating system for internal combustion engine
Abstract
An engine valve operating system of an electromagnetic type is
arranged to locate a movable member between two electromagnets
through a distance block and to connect the two electromagnets
through side walls. By alternately energizing the electromagnets,
the movable member is reciprocated against spring forces of two
springs. An engine valve is interlocked with the movable member and
operates according to the reciprocal movement of the movable
member. The side wall and/or distance block is made of soft
magnetic material and forms a magnetic circuit penetrating a side
surface of the movable plate. This new magnetic circuit increases
the attracting force of the electromagnet when a clearance between
the movable member and the electromagnet is greater than a
predetermined clearance. This arrangement decreases energy
consumption for the initializing operation of the valve operating
system from a neutral position between the electromagnets.
Inventors: |
Yonekura, Koichiro;
(Kanagawa, JP) ; Adachi, Hidefumi; (Ibaraki,
JP) ; Hoshi, Yoshikazu; (Ibaraki, JP) |
Correspondence
Address: |
Richard L. Schwaab
FOLEY & LARDNER
Suite 500
3000 K Street, N.W.
Washington
DC
20007-5109
US
|
Assignee: |
Nissan Motor Co., Ltd.
|
Family ID: |
18628356 |
Appl. No.: |
09/814689 |
Filed: |
March 15, 2001 |
Current U.S.
Class: |
123/90.11 |
Current CPC
Class: |
F01L 9/20 20210101 |
Class at
Publication: |
123/90.11 |
International
Class: |
F01L 009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 18, 2000 |
JP |
2000-116966 |
Claims
What is claimed is:
1. An engine valve operating system for an internal combustion
engine, comprising: a movable member interlocking with an engine
valve of the engine; a first electromagnet moving said movable
member in a valve opening direction when said first electromagnet
is energized; a second electromagnet moving said movable member in
a valve closing direction when said second electromagnet is
energized; a first spring installed to the engine valve, said first
spring applying a force directed in the valve opening direction to
said movable member; a second spring installed to said movable
member, said second spring applying a force directed in the valve
closing direction to said movable member; and a magnetic-circuit
member connected to said first electromagnet and said second
electromagnet, said magnetic-circuit member being made of soft
magnetic material, said magnetic-circuit member and one of said
first and second electromagnets forming a magnetic circuit when a
clearance between said movable member and the one of said first and
second electromagnets is within a predetermined range, the magnetic
circuit passing magnetic flux from said movable member to said
magnetic-circuit member.
2. The engine valve operating system as claimed in claim 1, wherein
the predetermined range of the clearance is smaller than a half of
a stroke of said movable member.
3. The engine valve operating system as claimed in claim 1, wherein
said magnetic-circuit member is disposed outside of a moving area
in which said movable member reciprocally moves between said first
and second electromagnets.
4. The engine valve operating system as claimed in claim 1, wherein
said magnetic-circuit member includes a pair of side walls which
are installed to side surfaces of said first and second
electromagnets while ensuring a predetermined clearance with
respect to side surfaces of said movable member.
5. The engine valve operating system as claimed in claim 1, wherein
said magnetic-circuit member includes a distance block which is
disposed between said first and second electromagnets to form a
predetermined clearance between said first and second
electromagnets.
6. The engine valve operating system as claimed in claim 1, wherein
a clearance between said movable member and said fixing member
becomes the smallest when said movable member is located at a
neutral position between said first and second electromagnets.
7. The engine valve operating system as claimed in claim 5, wherein
said movable member is in a form of rectangular plate whose main
surfaces are faced to said first and second electromagnets, and two
opposite side surfaces of said movable plate are faced to two
distance blocks, respectively.
8. The engine valve operating system as claimed in claim 7, wherein
the two distance blocks are arranged on a plane perpendicular to an
axis of a crankshaft of the engine when the engine valve operating
system is equipped on the engine.
9. The engine valve operating system as claimed in claim 1, wherein
the soft magnetic material includes iron, Permalloy, iron-nickel
alloy and silicon steel
10. The engine valve operating system as claimed in claim 5,
wherein the distance block has a pair of projecting portions which
are formed on the distance block so as to face to said movable
member.
11. The engine valve operating system as claimed in claim 10,
wherein a vertical dimension of the projecting portion is set to be
greater than a difference between the vertical dimension of the
distance plate and the vertical dimension of said movable
plate.
12. The engine valve operating system as claimed in claim 1,
wherein each of said first and second electromagnets comprises an
electromagnetic core and a pair of end block connected to the
electromagnetic core.
13. The engine valve operating system as claimed in claim 12,
wherein the end blocks and the distance block are partially made of
soft magnetic material such as iron such that the parts made of
soft magnetic material have a width corresponding to a width of
inner magnetic pole of said electromagnet, and the other parts of
the end block 9 and the distance block are made of non-magnetic
material.
14. An engine valve operating system for an internal combustion
engine, comprising: a movable member comprising a movable plate and
a shaft whose an end is integrally connected to the movable plate,
the other end of the shaft being in contact with a top end of an
engine valve; a first electromagnet fixed to a cylinder head of the
engine, the shaft of said movable member slidably penetrating said
first electromagnet in a direction perpendicular to an axis of a
crankshaft of the engine, said first electromagnet moving said
movable member in a valve opening direction when said first
electromagnet is energized; a second electromagnet fixed on said
first electromagnet through a pair of distance blocks to form a
predetermined clearance between said first and second
electromagnets, said second electromagnet moving said movable
member in a valve closing direction when said second electromagnet
is energized; a first spring installed to the engine valve, said
first spring applying a force directed in the valve opening
direction to said movable member; a second spring installed to said
movable member, said second spring applying a force directed in the
valve closing direction to said movable member, the force of said
second spring being balanced with the force of said first spring
when said movable member is located at a neutral position between
said first and second electromagnets and when said first and second
electromagnets are deenergized; and a fixing member connected to
said first electromagnet and said second electromagnet, said
magnetic-circuit member being located outside of said movable
member while having a predetermined clearance with respect to said
movable member, said magnetic-circuit member being made of soft
magnetic material, said magnetic-circuit member and one of said
first and second electromagnets forming a magnetic circuit when a
clearance between said movable member and one of said first and
second is smaller than a half of a full stroke of said movable
member, the magnetic circuit passing magnetic flux from said
movable member to said magnetic-circuit member.
15. An engine valve operating system for an internal combustion
engine, comprising: valve interlocking means for interlocking with
an engine valve of the engine; opening force generating means for
moving valve interlocking means in a valve opening direction when
said closing force generating means is energized; closing force
generating means for moving said valve interlocking means in a
valve closing direction when said valve interlocking means is
energized; first biasing means for applying a force directed in the
valve opening direction to said valve interlocking means; second
biasing means for applying a force directed in the valve closing
direction to said valve interlocking means; and magnetic-circuit
means for forming a magnetic circuit of passing magnetic flux from
said valve interlocking means to said magnetic-circuit means in
conjunction with said interlocking means and one of said opening
force generating means and said closing force generating means when
a clearance between said interlocking means and the one of said
opening force generating means and said closing force generating
means is within a predetermined range.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an engine valve operating
system for an internal combustion engine, and more particularly to
an engine valve operating system which operates engine valves of an
internal combustion engine by means of an electromagnetic force
generated by alternately energizing two electromagnets.
[0002] Various electromagnetic valve operating systems for
operating engine valves have been proposed. Generally such
electromagnetic valve operating systems require larger electric
energy in an initializing operation for starting the valve
operation as compared with the electric energy required during a
valve operating period. A Japanese Patent Provisional Publication
No. 58-213913 discloses an initialization method which largely
improves the energy consumption necessary for executing the
initializing operation of the engine valve.
SUMMARY OF THE INVENTION
[0003] However, this initialization method is required to further
certainly execute the initializing operation even if the
electromagnet type valve operating system employing this method is
put in any condition.
[0004] It is therefore an object of the present invention to
provide an engine valve operating system which is arranged to
increase the attracting force of electromagnets and decrease the
energy consumption during the initializing operation.
[0005] An engine valve operating system according to the present
invention is for an internal combustion engine and comprises a
movable member, first and second electromagnets, first and second
springs, and a magnetic-circuit member. The movable member
interlocks with an engine valve of the engine. The first
electromagnet moves the movable member in a valve opening direction
when the first electromagnet is energized. The second electromagnet
moves the movable member in a valve closing direction when the
second electromagnet is energized. The first spring is installed to
the engine valve and applies a force directing in the valve opening
direction to the movable member. The second spring is installed to
said movable member and applies a force directing in the valve
closing direction to the movable member. The magnetic-circuit
member is connected to the first electromagnet and the second
electromagnet. The magnetic-circuit member is made of soft magnetic
material. The magnetic-circuit member and one of the first and
second electromagnets forms a magnetic circuit when a clearance
between the movable member and the one of the first and second
electromagnets is within a predetermined range. The magnetic
circuit passes magnetic flux from the movable member to the
magnetic-circuit member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1A is a cross sectional view of an engine valve
operating system according to a first embodiment of the present
invention, and
[0007] FIG. 1B is another cross sectional view of the engine valve
operating system of FIG. 1A.
[0008] FIG. 2 is a cross sectional view taken in the direction of
the arrows substantially along the line II-II of FIG. 1A.
[0009] FIG. 3 is a cross sectional view taken in the direction of
the arrows substantially along the line III-III of FIG. 1A.
[0010] FIG. 4 is a graph showing a relationship of an attracting
force of an electromagnet and a spring force with respect to air
gap between a movable plate and an electromagnet.
[0011] FIG. 5 is an enlarged cross sectional view for explaining a
magnetic circuit generated by the electromagnet, the movable plate,
and side walls.
[0012] FIG. 6 is a graph showing an advantage of the first
embodiment according to the present invention.
[0013] FIG. 7A is a cross sectional view of an engine valve
operating system according to a second embodiment of the present
invention, and
[0014] FIG. 7B is another cross sectional view of the engine valve
operating system of FIG. 7A.
[0015] FIG. 8A is a cross sectional view showing a magnetic circuit
generated when the movable plate is located near the electromagnet
in the second embodiment, and
[0016] FIG. 8B is another cross sectional view showing a magnetic
circuit according to the present invention when the movable plate
is apart from the electromagnet.
[0017] FIG. 9 is an enlarged cross section view showing a distance
block employed in a third embodiment according to the present
invention.
[0018] FIG. 10 is an enlarged cross section view showing a
relationship between the distance block and the movable plate
employed in a fourth embodiment according to the present
invention.
[0019] FIG. 11 is an exploded perspective view showing the
electromagnet, an end block and the distance block which are
employed in a fifth embodiment according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Referring to FIGS. 1A to 6, there is shown a first
embodiment of an engine valve operating system for an internal
combustion engine in accordance with the present invention.
[0021] As shown in FIGS. 1A and 1B, a valve 2 for intake valve or
exhaust valve is installed to an intake or exhaust port 1a of a
cylinder head 1 of the engine. Valve 2 is slidably installed to
cylinder head 1 through a guide 5 embedded in cylinder head 1. A
retainer 3 for receiving an end of a valve spring 4 is provided at
an upper portion of valve 2. Valve spring 4 is provided between
retainer 3 and cylinder head 1 while being biased in a compressed
condition. Valve spring 4 biases valve 2 toward a direction for
closing the port 1a.
[0022] A bottom piece 6 functioning as a base of a valve drive
mechanism is installed to cylinder head 2 so that a lower half
portion of bottom piece 6 is embedded in cylinder head 2. An
electromagnet 7 for opening valve 2 during an energized condition
is installed on the bottom piece 6.
[0023] Electromagnet 7 is produced by winding an electromagnetic
coil 7a to grooves of a core having a E-shaped cross section and by
fixedly installing end blocks 9 and 10 to both ends of
electromagnetic coil 7a. A shaft 16 penetrates a center portion of
electromagnet 7 and is slidable with respect to electromagnet 7. A
movable plate 15 is fixed to an upper end of shaft 16 and is made
of soft magnetic material such as iron. A lower end portion of
shaft 16 is in contact with a tope end 2a of a stem of valve 2 as
shown in FIG. 1A so that movable plate 15 can interlock with valve
2.
[0024] An electromagnet 8 for closing valve 2 during an energized
condition is installed opposite to electromagnet 7 through movable
plate 15. The structure of electromagnet 8 for closing valve 2 is
constituted by an electromagnetic coil 8a and end blocks 11 and 12.
The structure is basically the same as that of electromagnet 7 for
opening valve 2 except that electromagnet 8 for opening valve 2 is
inversely arranged with respect to a horizontal plane perpendicular
to an axis of shaft 16 as compared with electromagnet 7 for closing
valve 2. Electromagnets 7 and 8 are fixed to have a predetermined
clearance therebetween by providing distance blocks 13 and 14
therebetween while movably locating movable plate 15 in the
predetermined clearance.
[0025] An upper spring shaft 17 penetrates a center portion of
electromagnet 8 and is slidable with respect to electromagnet 8. An
upper surface of movable plate 15 is connected to a lower end of
upper spring shaft 17, and an upper-spring retainer 18 is fixedly
installed to an upper end portion of upper spring shaft 17. A top
piece 20 of a body part of the valve operating system receives an
end of an upper spring 19 through a spring receiver 21. Upper
spring 19 for opening valve 2 is disposed between upper-spring
retainer 18 and spring receiver 21 while being put in a compressed
condition.
[0026] When both electromagnets 7 and 8 are put in deenergized
condition, movable plate 15 is kept at a neutral position between
both electromagnets 7 and 8 due to valve spring 4 and upper spring
19. Further, when electromagnet 7 for opening valve 2 is energized,
electromagnet 7 attracts movable plate 15 in the valve opening
direction against the spring force of valve spring 4 to open valve
2. When electromagnet 8 for closing valve 2 is energized,
electromagnet 8 attracts movable plate 15 in the valve closing
direction against the spring force of upper spring 19 to close
valve 2.
[0027] Bolts 24 penetrate top piece 20, eng block 12 fixed to
electromagnet 8, distance plate 14, end block 10 fixed to
electromagnet 7 and bottom piece 6, and fixedly connect these
elements to cylinder head 1.
[0028] Side walls 22 and 23 are made of soft magnetic material such
as iron, and are installed to side surfaces of the E-shaped cores
of the respective electromagnets 7 and 8 while ensuring a
predetermined clearance with respect to the side surfaces of
movable plate 15, as is clearly shown in FIG. 1B.
[0029] Movable plate 15 and electromagnets 7 and 8 are formed into
a rectangular shape, respectively, as viewed from an upper side and
as shown in FIGS. 2 and 3. The longitudinal direction of the
rectangular of these elements 15, 7 and 8 is the same as a
perpendicular direction perpendicular to an axial direction of a
crankshaft of the engine. Therefore, distance blocks 13 and 14 are
oppositely disposed to face to both short sides of movable plate 15
as shown in FIGS. 1A and 2, and therefore, distance blocks 13 and
14 are disposed along the perpendicular direction with respect to
the crankshaft when the valve system is installed to the
engine.
[0030] Next, there will be discussed the manner of operation of the
engine valve operating system according to the present
invention.
[0031] FIG. 4 shows characteristics of electromagnet 7, 8 of a
plate type and the spring employed in this embodiment. More
specifically, FIG. 4 shows a relationship between an attracting
force of electromagnet 7, 8 to movable plate 15 and an air gap
between electromagnet 7, 8 and movable plate 15 and a relationship
between a spring force of the spring and the air gap under a
condition that a predetermined electric current I.sub.0 is applied
to electromagnet 7, 8. Curve a of FIG. 4 shows the attracting force
of electromagnet 7, 8 with respect to the air gap, and curve b of
FIG. 4 shows the spring force of the spring with respect to the air
gap.
[0032] As is clearly shown in FIG. 4, electromagnet 7, 8 generates
a large attracting force when the air gap, which is a distance
between movable plate 14 and the surface of electromagnet 7 or 8,
is very small. Further, when the air gap is relatively large, the
attracting force radically decreases. Therefore, the attracting
force of the electromagnet 7, 8 under current I.sub.0 is balanced
with the spring having a composite spring constant k which is a
resultant constant of upper spring 19 and valve spring 4, at two
balancing points P and Q. The balancing pointy P is an unstable
balancing point, and therefore if the position of movable plate 15
shifts any quantity from the point P, the composite force of the
attracting force and the spring force acts to increase the shifted
quantity with respect to the point P. In contrast to this, the
balancing point Q is a stable balancing point, and therefore even
if the position of movable plate 15 shifts from the point Q by a
predetermined quantity, the composite force acts to return the
movable plate 15 to the point Q.
[0033] Accordingly, the attracting force of electromagnet 7, 8
becomes greater than the spring force when one of electromagnets 7
and 8 is switched off during normal operation and when movable
plate 15 is moved by simple harmonic motion to a position which is
nearer than the point P with respect to the other of electromagnets
7 and 8. Therefore, the valve operating system (valve actuator) can
attract the movable plate 15 under this condition.
[0034] On the other hand, when the initialization of the actuator
is started, movable plate 15 first stays at the neutral position S.
Under this condition, even if an electric current I.sub.0 is
applied to one of electromagnets 7 and 8, movable plate 15 merely
moves to at most the point Q. Since the point Q is the stable
balancing point, even if movable plate 15 is further moved near the
electromagnet, movable plate 15 is returned to the point Q by the
spring force larger than the attracting force of the
electromagnet.
[0035] In order to achieve the initialization of the valve
operating system, it is necessary that movable plate 15 is put in
the attracted condition where movable plate 15 is attracted to
electromagnet 7 or 8. That is, it is necessary to apply an electric
current I.sub.1 larger than the electric current I.sub.0 to the
electromagnetic coil. Although the current I.sub.0 is sufficiently
large to execute the normal valve opening and closing operation,
the initialization requires the current I.sub.1 larger than the
current I.sub.0. Therefore, it is necessary to provide a power
source and a drive circuit for supplying such electric current
I.sub.1, if the valve operating system is constructed
conventionally without side walls 22 and 23 of soft magnetic
material.
[0036] As mentioned above, the engine valve operating system for
operating valve 2 in accordance with the present invention
comprises side walls 22 and 23. Accordingly, the engine valve
operating system having side walls 22 and 23 ensures the following
advantages.
[0037] The attracting force characteristic of the electromagnet 7
shown by the curve a in FIG. 4 is ensured by the magnetic circuit
shown by A in FIG. 5.
[0038] By installing side walls 22 and 23 of soft magnetic material
at side surfaces of the plate type electromagnet 7 having an
E-shaped cross-section, a new magnetic circuit of magnetic flux is
generated as shown by arrows B in FIG. 5 when a distance between
electromagnet 7, 8 and movable plate 15 is greater than a first
predetermined distance. The magnetic circuit shown by the arrow B
circulates in the order of the inner magnetic pole of electromagnet
7, air gap, a lower surface of movable plate 15, a side surface of
the movable plate 15, side wall 22 or 23 and the outer side of
electromagnet 7.
[0039] The reason for generating the new magnetic circuit B is that
when the distance between movable plate 15 and electromagnet 7 is
relatively large, the magnetic resistance of the magnetic circuit B
becomes smaller than that of the magnetic circuit A. On the other
hand, when movable plate 15 sufficiently approaches electromagnet
7, the magnetic resistance of the magnetic circuit A becomes
smaller than a second predetermined distance. Therefore, when the
air gap between movable plate 15 and electromagnet is zero or
sufficiently small, the magnetic circuit A generates the attracting
force as same as the attracting force a of the normal plate type
electromagnet.
[0040] Due to the function of the magnetic flux B, the attracting
force of electromagnet performs the attracting force shown by curve
e in FIG. 6 so as to become larger than the attracting force of a
normal plate type without side walls 22 and 23, in the relatively
large gap region. More specifically, the function of the first
embodiment according to the present invention is explained as
follows:
[0041] First, it is considered as to a case that no side wall 22,
23 is provided to the actuator. When no side wall 22, 23 is
provided, only the magnetic circuit A shown in FIG. 5 is generated
under that condition that there is no leakage of magnetic flux and
the dispersion of the magnetic flux is equivalent in the
magnetic-circuit cross section and the saturation of magnetic field
of material is neglected. When the air gap is g, the magnetomotive
force NI and the magnetic field Hg in the air gap have a
relationship represented by the following equation (1).
NI.congruent.2H.sub.g.multidot.g (1)
[0042] The equation (1) shows that almost of magnetomotive force NI
of electromagnet coil 7a generates the magnetic field at the air
gap.
[0043] By utilizing the equation (1), the attracting force F1
applied to movable plate 15 is represented by the following
equation (2):
[0044]
F.sub.1=2KB.sub.g.sup.2S.sub.a=2.mu..sub.0.sup.2KH.sub.g.sup.2S.sub-
.a 1 F 1 = 2 KB g 2 S a = 2 0 2 KH g 2 S a 1 4 0 ( NI ) 2 S a g 2 (
2 )
[0045] In this equation (2), .mu..sub.0 is the permeability in
vacuum space, K is a proportion constant (K=1/(2.mu..sub.0), Bg is
a magnetic flux density at the air gap, and Sa is an inner magnetic
pole area of electromagnet 7. Similarly, an outer magnetic pole
area of electromagnet 7 is Sa.
[0046] On the other hand, in case that there are provided side
walls 22 and 23, the magnetic circuit B is formed as shown in FIG.
5. Therefore, when a clearance between movable plate 15 and side
walls 22 and 23 is d, the magnetomotive force NI and the magnetic
field Hg in air gap have a relationship shown by the following
equation (1)'
NI.congruent.2H.sub.g.multidot.g+H.sub.d.multidot.d (1)'
[0047] In this equation (1)', Hd is a magnetic field at a
clearance.
[0048] By utilizing the equation (1)', the attracting force F2 in
case of providing side walls 22 and 23 is represented by the
following equation (2)':
F.sub.2=KB.sub.g.sup.2S.sub.a=.mu..sub.0.sup.2KH.sub.g.sup.2S.sub.a
[0049] 2 F 1 = KB g 2 S a = 2 0 2 KH g 2 S a 1 4 0 ( NI - H d d ) 2
S a g 2 , ( 2 )
[0050] By comparing the equation (2) and the equation (2)', it
becomes clear that the attracting force in the case of providing
side walls 22 and 23 gradually approaches twice the attracting
force in the case of no side wall 22 and 23 as the clearance d
between the movable plate 15 and side wall 22, 23 sufficiently
decreases.
[0051] The initializing operation for attracting movable plate 15
from the neutral position S requires the large attracting force
under the condition that the air gap is large. Therefore, by
providing side walls 22 and 23 in contact with electromagnet 7, 8,
the initializing operation can be executed by the electric current
I.sub.2 smaller than the electric current I.sub.1 required when the
actuator having no side wall starts the initializing operation.
Accordingly, this arrangement is capable of decreasing the energy
consumption of electromagnets 7 and 8, of decreasing the size of
electromagnets 7 and 8 by decreasing the diameter of wire employed
in electromagnetic coil, and of employing small and inexpensive
drive circuits by decreasing the current capacity of electromagnet
drive circuit or electric wires.
[0052] Referring to FIGS. 7A to 8, there is shown a second
embodiment of the engine valve operating system according to the
present invention.
[0053] As shown FIGS. 7A and 7B, the engine valve operating system
of the second embodiment is different from the first embodiment in
that end blocks 9 and 10 for fixing electromagnet 7, end blocks 11
and 12 for electromagnet 8, and distance blocks 13 and 14 for
forming a space between electromagnets 7 and 8 are made of soft
magnetic material such as iron, instead of employing side walls 22
and 23. That is, the second embodiment does not employ side walls
22 and 23. The other construction of the engine valve operating
system of the second embodiment is the same as that of the first
embodiment. The shapes of movable plate 15, electromagnets 7 and 8
and distance blocks 13 and 14 are basically the same as those shown
in FIGS. 2 and 3.
[0054] In this second embodiment, when movable plate 15
sufficiently approaches electromagnet 7, 8, the attracting force
applied to movable plate 15 becomes the same as that formed by the
magnetic circuit A in the first embodiment.
[0055] On the other hand, when movable plate 15 is relatively apart
from electromagnet 7, 8, a magnetic circuit is generated as shown
by arrows C in FIG. 8B. The magnetic circuit shown by the arrow C
circulates in the order of the inner magnetic pole of electromagnet
7, the air gap, a lower surface of movable plate 15, a side surface
of the movable plate 15, distance block 13 (14), end block 9 (10,
11, 12) and the outer side of electromagnet 7. The magnetic circuit
C is formed around a center axis of movable plate 15 so as to
direct from electromagnet 7 to movable plate 15 through inside and
direct from movable plate 15 to electromagnet 7 through outside, as
shown in FIG. 8B.
[0056] This arrangement of the second embodiment similarly ensures
the advantages gained by the first embodiment. Since the second
embodiment is arranged by employing conventional structural parts
so as to form the magnetic circuit without providing side walls 22
and 23, it becomes possible to ensure the above mentioned
advantages without newly employing parts and increasing the size of
the system.
[0057] With reference to FIG. 9, a third embodiment of the engine
valve operating system according to the present invention will be
discussed hereinafter.
[0058] The third embodiment is arranged such that end blocks 9, 10,
11 and 12, and distance blocks 13 and 14 are made of soft magnetic
material, which is basically the same as the second embodiment.
Further, the third embodiment is particularly arranged such that a
projecting portion 13a, 14a is formed on a surface of distance
block 13, 14 faced to movable plate 15 as shown in FIG. 9.
[0059] By providing projecting portions 13a and 14a at surfaces of
distance blocks 13 and 14 directed to movable plate 15, the
magnetic flux of the magnetic circuit C is concentrated to
projecting portions 13a and 14a. This arrangement improves the
attracting force of electromagnet 7, 8 under the large air-gap
condition and can decrease the electric energy consumption.
[0060] With reference to FIG. 10, a fourth embodiment of the engine
valve operating system according to the present invention will be
discussed hereinafter.
[0061] The fourth embodiment is basically the same as the third
embodiment shown in FIG. 9. The fourth embodiment is particularly
arranged such that projecting portions 13a and 14 are located at a
center of a vertical dimension C of distance block 13, 14 as shown
in FIG. 10. This arrangement enables the attracting forces of
respective electromagnets 7 and 8 to be equalized with respect to
movable plate 15 when the magnetomotive force is applied thereto.
Accordingly, even if the initializing operation is executed to move
valve 2 into closed direction or into open direction, the
initializing operation is smoothly executed regardless the moved
direction of valve 2.
[0062] Further, a vertical dimension (width) T of projecting
portion 13a (14a) is determined so as to be greater than a
difference between the vertical dimension (thickness) X of distance
plate 13 (14) and the vertical dimension (thickness) t of movable
plate 15 as represented by the following equation (3).
T>X-t (3)
[0063] By this arrangement, movable plate 15 is always overlapped
with projecting portion 13a, 14a partially. Accordingly, even if
movable plate 15 slightly rotates around shaft 16 during when
movable plate 15 is moved to operate valve 2, movable plate 15 is
never scratched with projecting portions 13a and 14a. Movable plate
15 smoothly reciprocates in the space between electromagnets 7 and
8.
[0064] With reference to FIG. 11, a fifth embodiment of the engine
valve operating system according to the present invention will be
discussed hereinafter.
[0065] The fifth embodiment is arranged such that end blocks 9, 10,
11 and 12, and distance blocks 13 and 14 are partially made of soft
magnetic material. More specifically, as shown in FIG. 11, only the
parts 9c and 13c of end block 9 and distance block 13 are made of
soft magnetic material such as iron. The width of the parts 9c and
13c corresponds to the width L of inner magnetic pole of
electromagnet 7. The other parts 9b and 13b of end block 9 and
distance block 13 are made of non-magnetic material.
[0066] In a conventional system, distance block 13 and end block 9
have not been designed so as to circulate the magnetic flux.
Rather, they have been generally made of non-magnetic material such
as aluminum alloy, nonmagnetic stainless steel so as not to relate
the magnetic circuit. Particularly, in order to decrease the mass
weight at the top of engine head, they have generally been made of
aluminum alloy.
[0067] In order to suppress the weight of engine head including the
valve operating system, end blocks 9, 10, 11 and 12 and distance
blocks 12 and 14 are partially made of soft magnetic material. By
partially employing soft magnetic material at the part having the
width L as same as the width of inner magnetic pole of
electromagnet 7, 8, and by employing non-magnetic material such as
aluminum alloy at the other part, the increase of the head weight
is suppressed. In these embodiments according to the present
invention, the soft magnetic material applicable to the system
according to the present invention includes iron (soft iron),
Permalloy, iron-nickel alloy and silicon steel.
[0068] The entire contents of Japanese Patent Application No.
2000-116966 filed on Apr. 18, 2000 in Japan are incorporated herein
by reference.
[0069] Although the invention has been described above by reference
to certain embodiments of the invention, the invention is not
limited to the embodiments described above. Modifications and
variations of the embodiment described above will occur to those
skilled in the art, in light of the above teaching. The scope of
the invention is defined with reference to the following
claims.
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